1. Field of the Invention
The present invention relates to vehicle wheels, and more particularly to run flat tires which can be used to operate a vehicle when there is a flat or deflated tire.
2. General Background and State of the Art
Lightweight Application—Light Trucks and S.U.V.'s
There are two main problems that exist in this art. One is that the weight of a single combined tire and wheel for the vehicles at issue here can exceed 100 pounds. Therefore, it can be very difficult if not impossible for an individual to dismount a flat tire and wheel from a vehicle and remount a spare tire, especially in adverse conditions in the field. It is therefore advantageous for a vehicle to be able to run on a deflated tire at least for a certain distance to deliver a passenger to a safe place to repair or replace the tire or change the vehicle.
The second problem also relates to safety. A tire may blow out due to a sudden impact or a faulty tire. Regardless of how a tire fails, however, the failure can cause the deflated tire to traverse freely or uncontrollably within the wheel rim, becoming twisted and unstable, which can cause the vehicle to roll over at normal speeds.
Conventional pneumatic tire and wheel combinations for automobiles and light trucks are based on a configuration of the rim that includes an outer rim (facing outward from the vehicle), an inner rim (facing inward), and a tire mounting well or drop smaller in diameter than the outer edges of the inner and outer rims. The mounting well lies in close proximity to one of the rim edges to facilitate easy mounting of the tire. For example, the mounting well may be near the inner rim of the wheel. The inner tire bead is placed into this mounting well, and then the outer tire bead is mounted within the outer rim. Then the inner tire bead is moved into position against the inner rim, and the tire is inflated. Mounting the tire in this way typically requires the assistance of special tools or equipment to allow the balance of the tire to be mounted within the wheel and rim section.
Aside from mounting the tire to the wheel, the mounting well has no other practical use. However, in the event of a tire failure such as a flat tire or a blow out, the deflated tire drops back into the mounting well. The deflated tire twists on itself and gathers in folds into the tire mounting well, so that the tire is no longer in smooth contact with the ground. The wheel cannot continue to roll over a tire that is twisted in this way. As a result, the vehicle is no longer operative.
Prior solutions to the above problems are now described. Run-flat tires have been manufactured by parties such as The Goodyear Tire & Rubber Co., which introduced an asymmetrical design to lock the tire bead in place relative to the wheel. This was done in approximately 1983. Further, one solution was a wheel having a solid inner wheel located within the tire. In approximately 1997, a manufacturer introduced another wheel under the acronym “PAV,” which translates as “Vertical Anchorage Tire.” The acronym PAV was changed to PAX in approximately 1998. The key elements of the PAX system are special wheels with unique tire bead locks and a solid insert that can fully support its shape under the vehicle's weight and permit the vehicle to continue rolling even without any tire pressure.
In 2002, Bridgestone Corporation and Continental Tire developed a different run flat tire. It was later abandoned since the equipment to mount and dismount the tires was specialized. It should be noted that in each of the above developments, the concentration was on passenger or sports car type vehicles having tires with a low aspect ratio (sidewall height divided by tread width).
All of the above concepts have been the subjects of considerable research and development by major tire manufacturers, which suggest that the issue is important, but to date these efforts have not met with great success. Additionally, there is little developed run-flat technology for larger tires (light trucks and S.U.V.'s) that possess different geometry and load ratings than passenger car tires.
In terms of bead-lock wheel technology, conventional automotive tires and rims are similar in the contour of the bead, thereby providing an airtight combination between the wheel and the tire. The most popular bead-lock wheel/rim concept for a run flat tire requires that the rim be altered on the outboard portion to provide a coaxial ring with a series of threaded holes near the inner circumference. This ring is generally welded to the altered rim. In such a case, the tire can be mounted to the wheel by hand or with mounting equipment. However, the outboard portion of the tire must be positioned to lie on top of the attached ring and aligned outside the threaded holes. A separate ring can then be fastened into position with bolts, clamping and compressing the tire beads to a non-leaking state, after which the tire is inflated. Wheels of this type seal in a manner contrary to the tire's original design and concept, and may be used for short durations, such as for racing, prior to chronic air leaking. However, they are not satisfactory for use with light trucks and S.U.V.'s.
The present invention is an improvement on existing bead-lock technology. It also relates to the technology of, and improves upon, a prior modular vehicle wheel as shown in U.S. Pat. No. 4,989,657 by the same inventor, issued on Feb. 5, 1991, entitled “Modular Vehicle Wheel.” In that patent, a two-piece modular automotive wheel includes a rear section having a relatively thick center portion and a thinner rim portion. The rear section is produced by a spin forging process to achieve the desired thickness at various locations. A registration surface is machined in the center portion. A front rim section is secured to the rear section at the registration surface. A locking ring, which may also be spun forged, may be secured to the front rim section to lock the bead of the tire. The content of U.S. Pat. No. 4,989,657 is hereby incorporated by reference.
Military Tactical Vehicle Run Flat Wheels
Another area of improvement in run flat wheels that the present invention addresses is military tactical vehicle wheels and the like. Conventionally, these wheels include a solid rubber interior tire inside the inflated tire. The vehicle can run on this solid interior tire for a limited distance if the inflated, exterior tire becomes flat. There are two main problems with such wheels. One is that mounting and dismounting and/or inserting and removing a deflated tire from such wheels requires a high level of skill, specialized equipment and an inordinate amount of time. This is principally due to the physical size of the existing solid rubber inner (run flat) tire ring which is 30% larger in diameter than the diameter of the hole in which it must fit (the hole in the center of the inflatable tire).
Specifically, the solid rubber inner run flat tire ring measures 661.37 mm or 26.0 inches in diameter with a 4.0 inch thick cross section. The opening in the center of the inflatable tire is about 17.0 inches in diameter. From a strictly geometrical and physical stand point, it is extremely difficult to insert a 26.0 inch diameter object into a 17.0 inch diameter hole, and it is equally difficult to remove the object intact. However, given sufficient time, effort, and specialized equipment, it is possible to perform the task. One method is to compress the existing solid rubber interior tire ring under several tons of static pressure to a contour befitting a 17.0-inch diameter hole. However, the fact that the task requires specialized equipment and skills contributes to the difficulty presented by a flat or deflated tire.
The second problem is related to time, i.e., the time required to change a deflated, run flat tire of the existing solid rubber ring type. Currently, the required time to disassemble and re-assemble a deflated or disabled tire is about five hours using existing methods.
It is therefore desirable to provide an improved wheel system that permits safer operation of a vehicle for a longer duration for light trucks and S.U.V.'s on one hand, and military vehicles on the other hand, in the event of a flat or blown out tire.
It is also desirable to provide a wheel system which, in the event of a flat or blow out, prevents contortion of the tire in the wheel well.
It is further desirable to provide a wheel system that can be mounted and dismounted without specialized equipment and with less time than prior systems.
It is also desirable to provide a wheel system which employs a bead lock system and a centering element.
These and other advantages may be achieved by the present invention, as will become readily apparent from the detailed description taken in conjunction with the accompanying drawings.